Dewaxing distillate oils



Patented Sept. 8, 1936 2,053,872 DEWAXING DISTILLATE OILS Samuel A.'Montgomery, Wood River, 111., as-

signor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application May 24,1934,

' Serial No. 727,311

2 Claims. (01. 196-19) (The latter is ,also objectionable because of its cost.) vIt has been found that the so-called Con- This invention relates to the separation of wax from lubricating oil stocks and the manufacture of low pour test oils and it pertains more particularly to a method of increasing filter rates and 5 oil yields.

The so-called propane dewaxing process is the most flexible-known method of separating wax from oils because it is applicable to oils fromall sources and oils of all viscosities. In all cases when propane is used as a diluent it has'been found that with proper refrigeration, wax crystals are formed which may be readily filtered from the diluted oil. The character of the wax in the various distillates varies with the distillation range,

paraffin wax being associated with light distillates,

petrolatum being associated with residual stocks, and mixtures of paraffin and petrolatum being associated with heavy distillates or long residuums. With filter naphtha is wasdiificult, if not impossible, to dewax heavy distillate oils without the addition of cellular filter aids, petrolatum, asphaltic material, naphthalene-wax, naph thalene-parafiin wax condensation products, etc.; with a propane diluent I find that the heavy distillate stocks are easily filterable without the addition of such materials and I have found that rapid filter rates and high oil yields are obtainable. I have found that light distillates present an unexpected problem in propane dewaxing because the wax associated therewith tends to separate out in large crystals which occlude oil, which causes the formation of a loose, bulky wax cake which contains considerable amounts of oil and which is rather difficult to filter. The pronounced crystal growth promoting eifect of propane ap- ,pea'rs to aggravate this situation, making it diflicult to handle these light stocks in ordinary filter presses of the pressure leaf type particularly. The object of my invention is to expedite the filtration of wax from light distillates, to increase the filter rates, to increase oil yields, to decrease the oil content of the wax cake, and to obtain a hard, dense wax cake without contaminating the distillate or wax with residual oil products, asphalts, or condensation product filter aids.

An object of my invention is to provide a lubricant with a low carbon residue and with a minimum tendency to deposit carbon in internal combustion engines. For this reason it is extremely important that I avoid the addition of nonvolatile substances such as residual oil products, asphaltic materials or synthetic filter aids which are prepared by condensing chlorinated paraffin with naphthalene by means of aluminum chloride.

radson c tendency of an oil to deposit carbon and that volatility of the oil is the significant factor.

arbon test is not a true index of the the An object of my invention, therefore, is to prepare my lubricating oils from distillate stocks only.

I have discovered that if small amounts of heavy distillates are added to light distillates, the character of the wax in the light distillates is reinarkably altered, so that it may be rapidly filtered in a propane dewaxing system to give large yields of finished lubricant. In making light lubricants, therefore, I use a distillate stock which is a little lighter than would benormally used and I blend with this stock a small amount'of heavy distillate. By this simple expedient I can increase the capacity of a propane dewaxin'g' plant as much as 100%. Furthermore, instead oi'using a" heavy distillate for blending purposes I may use the wax cake from a heavy distillate, in which case I- re cover the oil from this wax cake simultaneously with the dewaxing of the lighterstock. Other objects and advantageswill be apparent as the detailed description of my invention proceeds.

In describing the invention, I will refer to various S. A. E. (Society of Automotive Engineers) grades which may be defined as follows:

There is E. 40, 50,

no particular difficulty in filtering S. A. and l0 oils and my invention relates particularly to the filtering of S. A. E. 10 and 20 oils. As

an example of the results obtained by my improvement, a propane dewaxing plant was designed and built to dewax 860 barrels of oil per day, and there is no difficulty in obtaining this throughput with stock such as S. A. E. 50 Mid- Continent distillate.

The throughput of the plant, however, was decreased sometimes as much as 50% when lighter distillates were dewaxed. This is apparently due to the manner in which the wax crystallizes, and I have found that, by blending a heavier distillate with the light distillate, the throughput with light oils may be made to capacity.

more closely approximate the designed The addition of 10% by volume of S. A. E. 60 distillate to S. A. E. 10 distillate doubles the filter rate and increases the dewaxed oil yield about 13% over the rates and yields obtained on treated S. A. E. 10 distillate. Typical operating data follow:

Blend with S. A. E. 20 15% S. A. E.

Average filter rate (gal/sq. lt./hr.), first run after cleaning presses 0. 48 1.0 Average filter rate (gal/sq. lt./hr after about 10 runs 24' .6 Oil yield (percent by volume) I The filter rates on the light distillate containing 15% of S. A. E. 50 oil were practically as good as those obtained by filtering the S. A. E. 50 oil alone.

The advantage of my invention may be applied in dewaxing distillates of S. A. E. 30 and even S. A. E. 40 grades. For instance, a straight out of -85 viscosity at 210 F. compares with a blended stock containing 50% of 140-150 viscosity at 210 F. distillate and 50% of 130-140 viscosity at 130 F. distillate as follows:

Straight Blended S. A. E. 40 S. A. EAO

Average filter rate gaL/sq. it./hr.),first run siterclelning presses 0. 83 L 47 Avarcgefilter rate (gal./sq. lt./lir.), third and Iourth runs after cleaning presses '0. 49 g 0.98 Average 'filter rate (gal/so. it./hr.).. eighth f and tenth rims afterclenning presses 0. 37 0.57 Oil yield (percent by volume) 75 '80 a certain grade and I blend with that stock a small amount of heavy distillate or wax cake from the heavy distillate. For instance, in making an S. A. E. 20 stock I employ 85% of a stock with 130 viscosity at 130 F. and 15% of a stock with viscosity at 210 F., thereby making a blend of about 185 viscosity at F. With these blended distillates I can obtain filter rates as high as 1.5 gallons per square foot per filtering hour and in the propane dewaxing plant referred to, I can dewax from 700 to 800 barrels per day of S. A. E. 20 stock while formerly the average was only about 400 barrels per day. At the same time I obtain greater yields of dewaxed oil. The practice of my invention does not require the use of expensive condensation products and it does not contaminate the oil with residues, asphalts, and objectionable carbonaceous or carbon-forming materials. The light oils obtained are used to a large extent in blending after dewaxing to make oils of intermediate viscosity so that the blended oils obtained in either case are identical.

While I have described in detail preferred embodiments of my invention, it should be understood that I am not limited to said details except as defined by the following claims, which should be construed as broadly as the prior art will permit.

I claim:

1. The method of increasing filter rates in the propane dewaxing of S. A. E. 10 to S. A. E. 30 lubricating oil distillate stocks which comprises blending with said stocks a small amount of an S. A. E. 50 to S. A. E. 70 distillate stock prior to dewaxing.

2. The method of obtaining large yields of low pour point lubricating oils from light lubricating oil distillates which comprises blending a small amount of heavy lubricating distillate stocks therewith, crystallizing wax therefrom in propane solution, and filtering the crystallized wax from the propane-solution.

SAMUEL A. MONTGOIVEERY. 

